Fractionating column with removable trays



Jan. 19, 1954 Flled Jan l0, 1949 Jan. 19, 1954 c, Q, HURD 2,666,737

FRACTIONATING COLUMN WITH REMOVABLE- TRAYS Filed Jan. 1o, 1949 ,5 sheets-sheer 2 C arles O. Hurdv 5g //WM his Aiorneg Jan. 19, 1954 c. o. HURD 2,666,737

FRACTIONATING COLUMN WITH REMOVABLE TRAYS Filed Jan. 1o, 1949 i 5 sheets-sheer s Jan. 19, 1954 c. o. HURD FRACTIONATING COLUMN WITH REMOVABLE TRAYS Filed Jan. l0, 1949 5 Sheets-Sheet 4 lnvn+or= Charles O. Hurd his AHornzq- Jan. 19, 1954 c, o, HURD 2,666,737

FRACTIONATING COLUMN WITH REMOVABLE TRAYS Flled Jan l0, 1949 5 Sheets-Sheet 5 Fig. IO

Fq. Il

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Patented Jan. 19, 1954 FRACTIONATING' COLUMN WITH REMOVABLE TRAYS f Charles -O..Hurd,` Piedmont, Calif., assigner to Shell Development- Company,l San Francisco, Calif., a. corporation of Delaware Application January 10, 1949, Serial No. 70,024

14 (claims. l.v

' This invention relates. to fractionating columns havingremovable trays. Fractionating columns used. for .distillationl are commonly provided with, Y aplurality of horizontal-traysioften referredto asbubble plates) for retaining a vertical series of pools of distilling liquid, downspoutsfor transferringliquid downwardly from pool to pool and maintaining the desired. level within each pool, and vapor-liquid contactmeans such'as bubble caps andthe like for: bringing vaporfrom the .space above any poolv into intimate contact withl thefliquidyinthe;poolabove, whereby the vapors ascend countercurrently tothe liquid. Sometimes-1 the spaces above the trays-arepacked with looseibodie's .suchL as beads, cylinders, rings, etc. to` eflectfcontact betweenthevapor and liquid.

Largev columns are readily cleaned, repaired,`

andA disassembled; by Workmen, who `enter` the columnthrough manholes provided in the shell and-in they trays.` In small vertical columns, where'rthis-is.notvfeasible,iit is common to avoid the use of horizontal trays and tapaokthe entire column with a. continuous mass of looseA bodies which will effect contact-between descend.-v

ing liquid andascending vapor. Columns of intermediate-size haveheretoforebeen diicult, to

operate underfycertain. conditionsr becausethey; areatoo small; to; loeservicedin theV manner-oi largeA columns and arcieri-this reason not welli adaptedioruse withtrays and bubble. caps,- and. n

are tooglarge, to permit, the use.of-continuousbedsk of loose packing-material; due touneven, flow ofthe fluids, sometimes known as Vchanneling Further, it is sometimes desirable to equipsmall columnswith trays and bubblevcaps.

For ther foregoing reasons it isoften inconven-isnt.v or undesirable to seal theA trays containing bubble capsor packing materialto the column Wallby conventional Vmethod (suclras welding,;b 0lting to anges-or using packing rings orv fractionating columnhaving removable trays.

which can readily be removed from the end of the column, without the necessity of havingza workman enter the column; intendedior. columns of; small intermediatesiaes;

the: invention is; not limitedl tberetofandf can. bezof bubble caps in such columns, it isy also useful when loose packing is used.

A further object is to provide a fractionatingY column having a shell and a plurality of trayA unitsywhich may be inserted into the shell. and

removed therefromindividually (or in groups of two or more), each removable `unit being com'- pletewith downspouts and vapor-liquid contact means.

A further object is to` provide:airactionating; column with removable trays having. a dependable and easily assembled arrangement for sealing the spacesbetween adjacent traysgfrom each other to prevent bil-passing of stages by either vapors or liquid. c

A further object isg to provide. airaotionating column' having removable tray sections which' are sealed with vrespect to each other by liquid seals deriving liquid froml the materialbeingdistilled, whereby-theuse of packing material isobviated and the columnY may be made lentirely of. metal, ceramic,` or other hard and `durable Amate-- rial.

Still a further object is to provide a novel ar- `rangement for afractionating column having removable, liquid-sealedA tray sections,v wherein the number of stagesmay be increased by. subdividing thefcolumn into two or more portions and maintaining these portions different vapor pressures in the spaces between the shelly and theremovable sections.

Another object is v`toy provide a removable tray fraotionating. column whereinthe feed material may beintroduced at either end or at an inter-v partici; this. specication. and illustrating several specific embodiments by way of example,

I wherein:

Whiie particularli7 applied to; large; columns.; l Moreover; whilertlier` f irmentifm4 is .especially useful in enabling tueuse Fig. l is a vertical sectional view of a column` constructedaccordingto the invention, certain tray sectionsrand other parts being in elevation;

Fig. 2 'is an enlarged elevation-view; partly in section, of one of the removable tray sections;

Fig. 3 is an enlarged horizontal sectional View l Figs-filare fragmentary section-a1' views of intermediate parts of the column showing two alternate arrangements for introducing and withdrawing fluid from an intermediate pointin the column wherein the column is sub-divided into sections;

Fig. 9 is a fragmentary sectional view of an intermediate portion of a column containing modied. tray sections and illustrating a further modiiied arrangement for introducing or withdrawing material from an intermediate point;

Fig. 10 is a sectional view of a further modified form of tray sections without bubble caps; and

Fig. l1 is a fragmentary vertical sectional view of a modified column without liquid seals.

Briefly, according to the invention, the fractionating column comprises a plurality of superposed, freely removable tray sections having bubble caps or the like or loose packing material and liquid transfer means, such as downspouts, and sealed with respect to each other by any suitable means against by-passing flow of fluids. Bypassing flow of fluids is used in this specification to denote ilow of vapor or liquid from a tray or stage to another non-adjacent tray or stage by flow around an intervening tray. In the preferred embodiment these sections are contained within a vertically elongated shell, such as a cylinder of any suitable cross-sectional shape, e. g., polygonal or circular, and the sections are sealed with respect to one another independently of the shell. A preferred sealing arrangement comprises a supporting sleeve fixed to the bottom of each tray deck and adapted to rest on the tray deck of the next lower section and a liquid seal sleeve of somewhat larger diameter, either diverging upwardly, or of cylindrical shape, xed to the top 0f the tray deck. The liquid seal sleeve will surround the depending supporting sleeve of the section above, forming an annular trough or basin in which liquid from the section corresponding to the liquid seal sleeve is retained to form a liquid seal. The points or ring of contact of the supporting sleeve with the next lower tray section are thereby submerged in the liquid. Sealing may also be effected without liquid pools for instance by closely fitting engagement of the support sleeves with the adjacent lower trays; such a t may be improved by providing a packing ring at the ring of contact. It is evident that two or more tray decks, each provided with downspouts and bubble caps may be assembled more or less permanently prior to insertion into the column, and that such assembled trays, in combination, then form the individually removable sections referred to in this specification. Moreover, the expression bubble caps, as used herein, is intended to denote generically various types of mechanical vapor-liquid contact devices permitting vapor to rise through the tray deck and come into contact with the liquid on the tray for exchange of components between the vapor and liquid.

The interior of the shell, when used, is constructed to permit the free and unimpeded vertical movement of the tray sections therein, e. g., for insertion and removal from the top. While it is preferred to stack the tray sections freely within the shell the invention does not exclude the use of externally operable means for locking the sections to the shell. Such tray sections can be fabricated from any material desired, such as pressed steel, tube sections welded to plate, enamelled iron, ceramic, glass, or synthetic resins.

Referring to the drawings, and particularly to Figs. 1-5, the column comprises a cylindrical shell l B having a flange ruig I2 integral with the shell or welded or otherwisey fixed thereto at the bottom. The latter is bolted to a corresponding ange I3 on the top of a reboiler lil provided with a suitable heating coil (not shown) through which heating fluid may be circulated via conduits It and I8. When the charge is to be introduced into the reboiler it may be admitted through an inlet 20. Liquid bottoms or distillation residue may be withdrawn through an outlet 22, controlled by valve 213 which may, if desired, be controlled automatically by a level controller 26. The top of the reboiler has an annular plate 28 with an up-turned flange 39; this flange may, in certain cases, be omitted.

The tray sections may be of identical construction, save that the lowermost and uppermost sections have orices or ports in certain sleeves and the lowermost section may have a shorter sleeve. As shown in Fig. 2, each section has a tray deck 32; a depending, cylindrical supporting sleeve 345 at the bottom; an upright, upwardly diverging, frusto-conical liquid seal sleeve 3&3 at the top and having a peripheral lip or flange 38; one or more downspouts 49 welded to the deck and extending through it down to a level just above the bottom of the supporting sleeve 3ft and rising above the deck to a height corresponding to the intended liquid level; and a plurality of bubble caps e2, each cap having a vapor tube i4 welded to the deck and in communication through a hole (not shown) in the deck with the space beneath the deck, and rising to a level above the intended liquid level. Sleeves 31% and 36 may be formed separately and welded to the deck 32. The caps 42 are fixed to the vapor tubes and have serrated edges beneath the liquid level. While the liquid seal sleeve 36 is shown to be higher than the support sleeve 3Q, this is not in every case necessary, as will appear hereafter. For convenience in raising and lowering the sections through the column each section is further provided with a bail or stirrup 45 permanently secured to the top of the deck. The bails preferably extend to above the centers of gravity of the tray section.

The lowermost tray section, as shown in Fig. Il, has the supporting sleeve 34a of shorter length than the other sleeves, just sufficient to space the deck 32 from the top of the flange 3B, and has an orifice 48 formed in the liquid seal sleeve 36a near the bottom thereof. rEhe downspout of the bottom section may be longer and extends downwards to beneath the liquid level in the reboiler I4. The uppermost section, as shown in Fig. 5, has a shorter liquid seal sleeve 36h, which may be made of thin corrugated metal and serves primarily as a vapor seal and also to confine the liquid on the tray deck and does not afford a liquid seal with respect to any higher tray. This Sleeve has a wider lip, extending over the top edge of the shell le. The supporting sleeve 34h of the uppermost section has a pressure equalizing orice 5l) formed near the top thereof. The flanges 33 of all sections except the uppermost section may have positioning notches 52, as shown in Figs. 2 and 3 for engagement with suitable vertical guides, such as vertical angle bars 54 fixed to the inside of the shell.

The top of the column is closed by a removable dome 56, bolted to a ange 53 at the top, and sealing the flange of the sleeve 35h to the shell l It is provided with a vapor drawoff duct di) for conducting overhead vapors to a condenser wherein partial or complete condensation of the overhead. may be effected by cooling coilalnot sleeve 35h which is clamped tothe shell.

them successively ,by lmeans of cables ha via yconduits -64 fand 66. :Liquidgrelux is 'returned tothe top .of `the .column through reilux line itt, which extends VVto .beneath Vthe liquid level-on the top tray, at a'rate controlled by valve L'irland unreturned overhead product is taken oi at l2. Uncondensed vapors, :may be drawnofl at Ii the .feed is to 'be introduced at the top of the column .it may be admittedthroughapipe llt and Va1ve18.

vItwill .be evident from the construction described that the lowerm-ost tray section is sealed to the shellandreboiler and zissupported thereby and that all sectionsfhigherexcept the uppermost section :are supported by `.their sleeves .311 abythe next lower sections. The ,invention contemplates the use of .any-desired arrangement 'for-mounting the lowermost section, e. g., bolting to the iiangesl I2 and I3 asshownfor tray 32h in Fig.8. According `to the embodiment illustrated 'in l--5, it is supported by the Vannular plate 28 and sleeve 34a. The uppermost section is supportedin part by iitssupport sleeve 34h and inpart bythe seal As will be seenv presently,=it'is not essentialthat the sleeve 34h have a close A-lt with -the'declr of the second tray-(counting romthe'top), and it is, therefore, not essential that the'sleeve 3.519 be corrugated I he-tray sections can be lelfnphiced by lov hooks or'other automatic release engagement Vdeyvices which support the Ksections by their b-ails 4B. Similarly, after removing'the dome 5t. the tray 'sections can beraised successively by these samebails for inspection, cleaning, replacement or repair. f

YWhen the column is in operation a pool of liquid will `beaccumulatori on Veach tray vto the levels ofthe tops ofthe downspouts it (Yorslightly above these tops when a rapidrate of fiow occurs) as indicated'in Figs. sand 5. Some of this liquid will seep out under the edges of the support sleeves 34, Ma, or '34h to form annular pools in Athe spaces .between the seal sleeves and the support sleeves. Thel level to which "these annular poolsvwill riseis dependent upon the pressures acting on their respective surfaces (i. e.,

the pressures outside of the support sleeves 3d)- and the pressures acting on the surface of they liquid pool' vwithin the sleeves 35i. The former pressure is uniform throughout the height of the column because all ofthe spaces outside of the sleeves 3d are in communication with ,one another, it beingnoted in Fig. S that there is a lree space between the llip 33 and the wall oftheshell `f this pressure drop, herein designated as h (which maybe measured in inches of liquid) is indicatedr in Figs. 4 and 5 by a liquid level Within each downspout f5@ which is vslightly/"higher than the liquid on the tray. For example, in Fig. "5, the liquid'head h is :the diierence between the levels azand and nFig. `emetween the levels VVc and d, or. "between -f .and y. LBecause ci thisv progressive increase iniprcssure each annularpool 'below the 6 pool ofthe second section 4will stand :at ra .level higher y'than the liquid within ,sleeve 3'4 :by a distance equal to wheremI is the tray number counting Afrom the top. Thus, as shown in'Fig. 5, for the third-.tray 11:3 and the level o of the x.annular-pool has .a hight of h inches' above the level bfof thewliquid within the sleeve; in Fig. Il, at vthe bottom section, the level c is farther above the level d.

The liquid level in each of the seal Vsleeves must bebelow the lip ofthe respective sleeve 35-01' ,the column will notoperate eiiciently. The .number of trays which can be `used inthe column will, therefore, depend upon the lvalue of h in .relation to the heights of the liquid seal sleeves x36,

and it is, in certain cases, desirable to malrethese sleeves somewhat higher1 for Vthe lower sections. The number of trays can also be increased yby subdividingthe shell into severalsections, forexample as described for Figs. 7 and 8.

The lowerrnost section is, in the specic eml bodiment illustrated, sealed against the plate 2B contact with the material on `the higher Vitrays."

It thereby'prevents the pressure of the vvapor `in this annular space from rising. The exact level 7c will depend upon the closeness of the iitzof the sleeve 3ds against plate '28. made large in relation to the leakage space-around the .bottom of the sleeve (as-would occur when sleeve 34a 'has va smooth, close-fit with plate 23s) the level ktends to rise to the level c; the column can be successfully operated with such an arrangement. Ont-he other hand-it is-also possible to form the bottom of the sleevel with irregularitiesor serrations -to permita continual seepage of liquid into the reboiler yat arate'which is dependent uponthe size of the orifice G8 and the pressure difference c-7c.

Itis seen 'that the column .is self-sealing, that the liquid being Adistilled forms pools `preventing short-circuiting of liquid or vapor `between non-adjacent stages. The feature of sealing the sleeve 3th of the uppermost section ,to thecolumn isparticularly effective in preventing splashed lliquid rom the top section (Where splashing is most prevalent) from descending in the annular space immediately inside of the shell I0 and contaminating liquid of different composin between the sleeve 35h andthe-shell. 'Intnis embodiment ithe uppermost section is supported wholly on the next 'lower section by Vits `support sleeve A311e andthe uppermost liquid seal sleeve 35e is in engagement'with the positioning flange 5d Ahutnot sealedagainst'the shell if). The pressure acting ontlie annularpools within'theseal sleeves isithat of Ythe top'stage; Yhenceth'ese pools will stand above the liquids within the support sleeves 3.45 by distances equal .to fam- 1), vand the approximate minimum heighto'thelevel lcfabove the' iange :'39 is A useful 4character.isitic vof the column; apart lf the orifice e8 is from the ease with which it may be disassembled, is the excellent heat-insulating effect of the annular vapor space immediately inside of the shell l0, which is effective in reducing heat losses.

The embodiments described heretofore are suitable when the feed is to be introduced at the top or bottom end of the column and products are withdrawn at the top and bottom.

Liquid feed, particularly if cool, may be fed into one of the intermediate sleeves 3E for iiow into the tray deck associated therewith. Thus, as shown in Fig. 6, a feed pipe 'Vl may feed liquid into sleeve 35d, from which it passes into deck 32d through one or more large ports '19 in the sleeve 34C below the liquid level. Pipe 'll may be slidably mounted in the shell l@ to permit retraction when the tray sections are to be emplaoed or removed.

In columns using liquid sealed plates, it is, however, usually preferable to provide special arrangements if the feed is to be introduced at an intermediate point and/or side streams are to be Withdrawn at one or more intermediate points. A simple solution of this problem is to break the column into two or more sections at the level where a feed or drawoif pipe is to be fitted. Two alternate arrangements are shown in Figs. '7 and 8.

In Fig. 'l the lower section of the column has a shell Illa and the upper-section has a shell leb. A special intermediate shell section 8) is interposed between these sections. The intermediate shell section 81% is shown to be connected to the lower shell section 50a in much the same manner as the dome 56 was connected to the section I in Figs. 1 and 5. In other words, its flange 82 is detachably bolted to a flange ring Se which is at the top of the shell Ilia. The liquid seal ring 36e of the uppermost tray section in the lower shell IM (designated as having a tray deck 32e) is made of thin material and its annular lip is clamped between the flanges 82 and 34 to pro vide a seal; the corrugations shown in Fig. are omitted, in this case, but may be used. The supporting sleeve 34e of the uppermost tray section has a vapor port near the top. The section 80 has a feed line fitted thereto, extending to below the liquid level established by the downspout we and disposed to feed liquid onto the tray; it may also serve to withdraw liquid as an intermediate product or side stream. Instead of liquid, a vapor feed may be supplied through a vapor pipe 83; it may also be employed to withdraw vapors as a side stream. from the column. Either pipe or pipe 88 may be omitted, depending upon the speciiic use to which the column is to be put.

The top of the section 89 has an annular plate Sil with an inner, upturned iiange 92; these correspond to the plate 28 and iiange 30 of Figs. 1 and 4 and support the upper shell lllb and the upper tray sections in the same manner as the reboiler plate 28 supports the column It. In other words, the shell has a ange ring 9s at the bottom, which is bolted to the plate 8! and flange S5, and the lowermost tray section of the upper section of the column (indicated as having a tray deck Bf) has a short supporting sleeve 3M tting inside of flange s2, while its liquid seal sleeve 36j has an orice d8 for admitting liquid onto the top of the plate Si) to seal the higher tray sections of the column from vapors within the intermediate shell section B. The overiiow pipe or downspout lili of this tray section is longer than the others and extends into the liquid on the tray deck 32e. It should be understood that the top fil) of the shell section Illb may be provided with a dome according to any of the embodiments described herein, e. g., as shown in Fig. 5 or 6, and that the bottom of the shell section Illa may be supported on a reboiler as shown in Fig. 4. Moreover, several intermediate sections may be placed at various levels of the column.

The column according to Fig. 7 operates as follows: The tray sections within the upper shell 10b act as a rectifying section, while those within the lower shell Hla act as a stripping section. The pressure above the tray decks increases progressively from the top of shell Illb to the bottom of shell 10a. However, the annular space immediately inside of the upper shell ib and outside of the support sleeves therein is maintained at a lower pressure than the corresponding annular space within the lower shell lila. It is not to be implied however that these pressures can differ greatly, the pressure diiference being limited by the height to which the liquid can rise within the liquid seal sleeve 35j. Thus, the annular space in each shell is at a uniform pressure equal to that above the second tray section within its respective shell (for the embodiment shown in Figs. 5 and 7 wherein the top sections are sealed to their shells) As a result, the level of the annular pool of liquid outside of the support sleeve 314e is the same as that of the liquid inside of sleeve 36g, and lower annular pools stand at progressively higher levels above the liquid on the tray decks.

In Fig. 8 the column again comprises lower and upper shell sections lilo and Illb; these are separated by an intermediate shell section 95. The upper shell leb is constructed and operated as described above except that the lowermost tray section thereof comprising deck 32h is of direrent construction and has a flange extending out beyond shell et. It is supported and sealed and connected to the top of section S6 by being clamped between flanges 911 and d8 on the shells ltib and 9S, respectively. This deck need not have a bail or support sleeve; its downspout 48h extends about to the deck 327i of the lower section Eile. The latter' also of special design in that the tray deck Sii has an annular iange instead of the usual upright seal sleeve, said ange extending laterally over the upper edge of the shell its' and the flange ring es. The tray deck is thereby scaled against the shell when the flange lei) of the intermediate section is bolted to the ring e9. The tray deck 321' has the usual downspout dei and bubble caps 422', but requires no bail. If the flange of deck 321 is suiciently rigid the supporting sleeve Sei at the bottom of the deck may not always be in close engagement with the tray deck 32k of the next lower section; while this sleeve may, therefore, in certain cases be omitted, it is preferred to provide it both to insure spacing of downspout 9i from tray deck 32k and to prevent froth which forms on the deck 32k from spilling over the edge of seal sleeve 367C. The flange of deck 321' may optionally be made thin enough to insure contact of the supporting sleeve Siiwith deck 32k notwithstanding irregularities in the heights of the tray sections due to inexact manufacture or expansion due to temperature changes. Sleeve 341' has a port 50 near the top.

The intermediate section Wi has a pipe lill iitted into its side for drawing oir liquid from the deck 3%. When so used it is desirable to maintain a pool of liquid on this deck to a greater depth than on the other trays, and the downspout lili preferably rises to a correspondingly unused,connectionsare p-luggedor capped;-

erring to annate? greater distance above thedeck, as shownr The y pipe-ISI may also be used as a feed pipe; in this case the-higher level may not be needed and the downspout may rise to the Asame height above the tray asforthe other trays, e. g., as shown-for downspout tte in Fig. 7;l The lower tray sections are arranged within the shell lll-as de scribed for shell `l il iii-Figs'. 1 5; Y

The operation of the liquidY sealveler'nentsl in Fig. 8 is as was describedfor'Fig. 7. It is evi-y dent that in Figs. 7 and S'the"intermediate-secr tion 85 or -Qrinay in certain casesbe cast integrally with Yeither the upper or v'lower shell; and of aldiierent e. g., larger diameter. l l

According toanother arrangement i'orfeedingv distilland into anintermediate point of thev coli-` umn, as shown in Fig. 9; the tray sections are provided with lateralA connections which are in alignment with'ports in thefshell-wall,through which fee-d or discharge lines may be passed; The Re-V the drawing, there isshowh alshell se having handholes istat# various levels.y All or some of the tray sections are/provided withfeed spouts ist. Eachv spout has its discharge Vendf near the next lower tray deck and passes ythrough the supporting sleeve When not used they are closed by plugs les The liquid seal sleeves 350i these sections haveholes IE aligned with" the outer, upper ends of pipes H53, and normally closed by plugs ist." The shell itc has covers' lill closing the handholes at points where no con-` nection is made with the spouts H13: One or more selected covers lili'inay be removed for inserting one or more supply (or discharge)` pipes which have couplers at their inner ends. Thus, a supply pipe IESA can be coupled to one of the spoutsr As previously indicated, the invention canalso be applied to columns vwithout bubble caps. Thus, Fig. shows an alternatetype of-tray section having a perforated tray deckl 32%,;- Vapors ascending from a-lowertray section pass through'- small perforations i Mandi-prevent descento'fliquid therethrough, and cause a pool of liquid to collect to the level of-the Itop of downspout'm. The vapors are b-roughtlinto contact with liquid on the tray by bubbling therethrough.V These tray sections are-assembled within the shell' 'in the manner previously described for the sections provided with bubble. caps. I1 desired, loose v packing material may be placed on -the tray 32m,

the downspout dem being then unnecesary because liquid descends vthrough the` holes Ils, which may be madeA large enough to permit now of both-liquid and vapor.

The modi'cation shown inlFig.-11 dispenses with the liquid sealing arrangement and usesv tray sections whichmay be used withforwithout an outer shell. Such shellmay be desirable te"- add support to the vtray sections, to improve thermal insulation and/or to permit the' use of greater pressures or vacuum within the tra'ysections;V As shown, the column comprises an outershell vlcd connected to a reboilerfilland dome S6;- operate The supplypipe being thus sealed tothe be distilled.

ing aspreviously described. The reboiler shell carries an'annular support plate l l2A for supporting the tray deck l is-'o'f the'lowermos't tray section. Each tray'deck carries a depending supe' y port sleeve i is; the lower edge of which is shaped tonsure a liquid-tight seal with the next lower tray deck; The' support sleeve I hier of the lower'- niost section may be shorter and rests onthe -plate l 52. :Toimp'rove sealing thelower edges of the sleeves may be beveled to provide ya-narrow, or sharp annular edge,- and the tray deck'sand "plate H2 maybe provided with lannular grooves i5 containing' a vy'ieldable ring H6, e. g. madelof gasket material or of soft rnetalsuch as lead; de` pending niponthe corrosivity of the material to bottom of each groove H5 has two annular upward projections IH' to insure a liquid-tight seal. Each tray is further providedwith a downspout 59; bubble cap 42y and bail 46.-

" The uppermost tray deck Ha carries an upstandingliquid retaining sleeve H8 to prei/'ent splashed liquid andA froth fromspilling into the annular space immediately inside of the shell l 0d.AIA

It "will be noted that the difference btween the pressures inside and outside ofthe sleeves iid increases progressively toward thes bottom ofthe column.` The tightness ofthe seal of the1 sleeves l l@ against the adj acent lowertrayy decks is also progressivelyV more effective towardv i the bottom of the' column becausev each sleeve supports the weight of all superior sectionsfand liquid thereon. To still further improve the tightness tie rods H9, anchored'n'the plate H2', may be provided for' urging the uppermost deck H30, downward, thereby deforming the packing' rings l it and forming more effective seals. These" tie rods further serve as orientation guides for thery intermediate tray decks which have notches |'20 at their peripheries.

claim as my invention zV 1-. A fractionating column comprising: a closed` vertical shell having a top opening with a remov` able, fluid-tight closure and being adapted to maintain a pressure differential between the interior and exterior thereof; a plurality of at leastV three tray sections within said shell formingv a vertical series of contact stages, each section having a tray deck with passageways for the upward yilow of 'vapor and the downward flow of liquid` through the decks 'arranged to effect intimate contact between said liquid and vapor withalv pressure drop between stages; said tray sections being shaped to permit unimpeded vertical movement thereof as separate units through the shell to the'top thereof and through saidtop opening upon removal ofY saidy closure; a closed annular wallon each tray section extending in sealed re lation from the decir thereof vertically to a corresponding annular portion on an adjacent section, said walls'enclosing liquid and vaporconf tactv spaces within themselves, and the wall ,andA decks `or" at least av plurality of lower sectionsV having clearances' with respect to theshell to denne a common outer space between thegshell and said lower sections extending vertically through the height of severaltray sections; an-

annular seal between each annular walll and'its corresponding annular part on theadjacent section arranged to prevent' the outward flow of 'vali por from said contact' spaces into said oiiter space, each seal comprising atro'ughadapted to retain a pool of nquie that contacts the-inner' and outer sides of the annular wall,l whereby said seals can beestablished by successively low-r lerin'g tray f sections through the shellandsaid contact spaces can be maintained at progressively different pressures independent of the pressure in said outer space; seal means between the lowermost tray section and the shell closing oi the bottom of said outer space, whereby the pressure in said outer space is isolated from the pressure immediately beneath the tray deck of said lowermost tray section; and a vapor passageway interconnecting said outer space with one of the upper Contact spaces, whereby the pressure in said outer space will be that of said one upper contact space.

2. A fractionating column comprising: a closed vertical shell having a top opening with a removable, iluid-tight closure and being adapted to maintain a pressure differential between the interior and exterior thereof; a plurality of at least three separately removable tray sections within said shell forming a vertical series of contact stages, each tray section having a tray deck with passageways for the upward iiow of vapor and the downward now of liquid through the decks arranged to effect intimate contact between said liquid and vapor with a pressure drop between stages and to maintain a body of liquid on the deck and a vapor space above the body of liquid, the said tray sections being shaped to permit unimpeded vertical movement thereof as separate units through the shell to the top thereof and through said top opening upon removal of said closure; a supporting sleeve depending in sealed relation from each tray deck above the lowermost tray deck and resting releasably on the next lower tray section immersed in the body of liquid on the deck thereof; and a liquid Seal sleeve rising from each tray section in sealed relation thereto to a height above the body of liquid on the deck thereof by a distance exceeding the product of h, and (1L-2), wherein h is the liquid head corresponding to the said pressure drop between adjacent stages and 11. is the number of the tray section counting from the top, each liquid seal sleeve having a diameter greater than that of the support sleeve of the adjacent higher section to form an annular trough for a pool of liquid surrounding the said support sleeve, thereby providing a liquid seal permitting the vapor spaces of progressively lowerl trays to be maintained at progressively greater pressures, and said tray sections and sleeves providing a clearance with respect to the shell to permit pressure equalization among the outer spaces at different levels between the shell and the several tray sections.

3. A fractionating column according to claim 2 wherein the uppermost tray section is sealed to the shell and the supporting sleeve thereof is provided with a passageway above the body of liquid on the adjacent lower tray deck for equalizing the pressure of the vapor space above said body of liquid and the pressure of the said Outer spaces, whereby the pressure ofI the said vapor space above the second tray deck is effective against the surfaces of said pools of liquid in each of the annular troughs.

4. A fractionating column according to claim 2 wherein the vapor space above the uppermost tray deck is in communication with the said outer spaces, whereby the pressure of the said vapor space above the uppermost tray deck is eiective against the surfaces of said pools of liquid in each of the annular troughs.

5. A fractionating column according to claim 2 wherein said shell has on the inside thereof a vertical guide and at least one tray section has a complementary guide shaped to prevent relative rotation between the tray section and the shell for maintaining the tray section in a predetermined orientation.

6. A fractionating column comprising: a closed vertical shell adapted to maintain a pressure diferential between the interior and exterior thereof; a plurality of at least three separately removable tray sections within said shell forming a vertical series of contact stages, each tray section having a tray deck with passageways for the upward fiow of vapor and the downward new of liquid through the decks arranged to effect intimate contact between said liquid and vapor with a pressure drop between stages and to maintain a body of liquid on the deck, said tray sections being shaped to permit unimpeded vertical movement thereof through the shell; a supporting sleeve depending in sealed relation from each tray deck above the lowermost tray deck and resting releasably on the next lower tray section immersed in liquid on the said lower section; and a liquid seal sleeve rising from each tray-section in sealed relation thereto and having a diameter larger than that of the supporting sleeve of the adjacent higher section, the liquid seal sleeve of at least some of the tray sections being taller than the supporting sleeves of the respectively adjacent higher tray section so as to surround the latter supporting sleeves for the full heights thereof, each liquid seal sleeve forming an annular trough for a pool of liquid about the supporting sleeve or" the adjacent higher section, thereby providing a liquid seal permitting the spaces above the several tray decks to be maintained at progressively different pressures, and said tray sections and sleeves providing a Clearance with respect to the shell to permit pressure equalization among the outer spaces at different levels between the shell and the several tray sections.

7. A fractionating column comprising: a closed vertical shell adapted to maintain a pressure differential between the interior and exterior thereof a plurality of at least three separately re movable tray sections within said shell forming a vertical series of contact stages, each tray section having a tray deck with passageways for the upward flow of vapor and the downward dow of liquid through the decks arranged to effect intimate contact between said liquid and vapor with a pressure drop between stages and to maintain a body of liquid on the deck, said tray sections being shaped to permit unimpeded vertical movement thereof as separate units through the shell; a supporting sleeve depending in sealed relation from each tray deck, the support sleeve of each section above the lowermost section resting releasably on the next lower tray section and being immersed in the liquid on the said lower section; a liquid seal sleeve rising from each tray section in sealed relation thereto and having a diameter larger than that of the supporting sleeve of the adjacent higher section, forming an annular trough fora pool of liquid about the supporting sleeve of the adjacent higher section, thereby providing a liquid seal permitting the spaces above the several tray decks to be maintained at progressively different pressures, and said tray sections and sleeves providing a clearance with respect to the shell to permit pressure equalization among the outer spaces at different levels between the shell and the several tray sections, said column having a vapor chamber immediately beneath the lowermost of said sections adapted to be maintained at a pressure higher than that the shell with saidsupport plate atthe bottom and open atthetop'to saidf outer spaces, the central opening of saidplate containing vapor; and liquid ilow communicating means between the space above the said lowermost tray deck and said lower annular trough for admitting liquid from said tray deck to said lower trough to pro'- mme? vide a liquid seal for preventing iow of vapor from the vapor chamber into said outer space.

8. Afractionating column according to claim'rl wherein'said annular support plate has an upstanding annular flange at the radially inner margin thereof inside oi'the support "sleeve of said lowermost tray section. y

9; A fractionating" column comprising a reboiler; 'an/annular'platefsealed to andv located above!` the reboiler, the central opening of said annular Eplate aiiordingy vapor communication with the interior'of the reboiler; an upright cylindrical shell having a top opening and sealed to the top-Y of said plate 'radially outwardly from said -central openingvga closure removably connected'to ,said top opening of the shell; means for-supplying a distillandto the column; means for withdrawing distillation bottoms from the column; and a plurality of separately removable tray sections within series of stages therein, each tray sectionfhaving a tray deck, a downspout and a bubble cap, the

lowermost tray section having adependent annular wall resting on said annular plate and tray sections superior thereto being supported each from a section inferior thereto, said shell and tray sections being shaped to permit unimpeded verf tical movement of the tray sections therethrough to the top; means independent of the shell for sealing adjacent tray sections with respect to one another from an outer space within the rshell and outside of the tray sections extending throughout the height of the said plurality of sections, whereby said sections can be maintained at progressively different pressures independent of the pressure in said outer space; and means for isolating said reboiler from said outer space against by-passing flow of fluids including said dependent annular wall on the lowermost section, said annular wall having vapor on the inside thereof opposite liquid on the outer side thereof, said liquid being a part of the liquid on the deck of the lowermost tray section, resting on said annular plate, and having the surface thereof exposed to the pressure in said outer space.

10. A fractionating column comprising upper and lower closed vertical shells sealed to one another at an intermediate level of the column, said shells having top openings and the upper shell having a removable, duid-tight closure, said shells being adapted to maintain differential pressures between their interiors and the exteriors thereof; a plurality of at least three tray sections within each of said shells separately removable from said shells as complete Aunits by vertical movement through their respective shells and forming vertical series therein, each tray section having a tray deck with passageways for the upward iiow Vof vapor and the downward flow of liquid through the decks arranged to effect intimate contact between said liquid and vapor with a substantial pressurerdrop between stages; walls said shell forming a vertical independent of and within said shells disposed to seal said tray sections with respect to one another against passage of fluids and having clearances with respectto-'said shell to form outer spaces between the shells andV the tray sections',

each of said outer spaces extending uninterruptedly. through the height of several trayy sections to have a substantially uniform pressure throughout said height while the pressures. within saidwalls abovethe several tra-y decksvareprogressively greater from the top of .the upper shell to ,thefbottom -of= the lower` shell; and means sup,- porting sealing the tray deck of the lowermost-tray section in the uppershell to thelower part of the upper shell, thereby isolating. the outer space of the upper shell from the outer Y space of the lower shell, each of said outer spaces beingV in vapor flow communication with onefof the spaces above one of the tWduppermosti tray decksi within the respective shell, whereby the outer space of said' lower shell can be maintained at a. greater pressure than the outer spaceofthe upper shell. Y y Y f 11.` A fractionating column comprising VVupper Y and'lower closed vertical shells sealed to one other at an intermediatelevel of fthe column, said shells having top openings andthe uppershell having a removable, fluid-tight closure, said shells being adapted to maintainl differential pressures between their interiors. andA the exteriors f thereof ;vr a plurality-of at. least three tray'.` sections within each of` said shells separately removable from said shells as complete unitsV by Vertical movement through their respective shells and` formingvertical series therein, each tray section having a tray deck with passageways for the upward ow of vapor and the downward flow of liquid through the decks arranged to eiect intimate contact between said liquid and vapor with a substantial pressure drop between stages; walls independent of and within said shells disposed to seal said tray sections with respect to one another against passage of fluids and having clearances with respect to said shell to form outer spaces betweenthe shells and the tray sections, each of said outer spaces extending uninterruptedly through the height of several tray sections to have a substantial uniform pressure throughout said heighty while the pressures within said walls above the` several tray decks are progressively greater from the top of the upper shell to the bottom of the lower shell; means supporting and sealing the tray deck of the lowermost tray section in the upper shell to the lower part of the upper shell, thereby isolating the outer space of the upper shell from the outer space of -the lower shell, whereby the outer space of said lower shell can be maintained at a greater pressure than the outer space of the upper shell, and conduit means at said intermediate level immediately'below the said means supporting and sealing the lowermost tray section of the upper shell establishing flow communication between the inside and outside of the column for the introduction or discharge of fluid. y

12. A fractionating column comprising an upper and a lower vertical shell sealed to one another at an intermediate level of the column; a plurality of separately removable tray sections within each of said shells forming vertical series therein, each tray section having a tray deck, a downspout and a bubble cap, said shells being shaped to permit unimpeded vertical movement of the tray sections contained within the respective shells to the tops of said sections; a support- 15 ing sleeve depending from each tray deck and sealed thereto and engageable with the next lower tray section to rest thereon; a liquid seal sleeve rising from each tray deck and sealed thereto and. having a diameter larger than that of the supporting sleeve of the adjacent higher section,

each of said liquid seal sleeves being spaced from the inside of its respective shell and forming an annular trough for a pool of liquid about the supporting sleeve of the adjacenthigher section to form a liquid seal; an annular plate within the column at said intermediate level sealed externally to said upper shell and affording support to the lowermost section of the upper shell and forming the bottom of an annular trough for pool of liquid surrounding the supporting sleeve of said lowermost section; and conduit means at said intermediate level and below said annular plate establishing ow communication between the inside and outside of the column for the ini 16 of the space abovethe tray deck of the second section of the lower shell and said pressure is eiective against the surfaces of said pools of liquid in the lower shell.

14. The fractionating column according to claim 12 wherein the shells are spaced apart vertically by an intermediate section, and the said conduit means extends through the side wall of said intermediate section.

CHARLES o. HURD.

References cited in the nie of this patent Y UNITED -STATES PATENTS Number Name Date 344,322 Lunge June 22, 1886 573,956 Bachman et al Dec. 29, 1896 729,121 Boby May 26, 1903A 852,487 Zscheck May 7, 1907 1,467,583 Lichtenthaeler Sept. 11, 1923 1,686,542 Winkler et al Oct. 9, 1928 1,711,656 Risdon May 7, 1929 1,889,254 Lea Nov. 29, 1932 2,241,370 Armstrong May 6, 1941 FOREIGN PATENTS Number Country Date 37,593 Germany Nov. 10, 1886 91,717 Germany May 6, 1897 24,598 Great Britain Dec. 24, 1914 295,365

Italy Apr. 19, 1932 

1. A FRACTIONATING COLUMN COMPRISING: A CLOSED VERTICAL SHELL HAVING A TOP OPENING WITH A REMOVABLE, FLUID-TIGHT CLOSURE AND BEING ADAPTED TO MAINTAIN A PRESSURE DIFFERENTIAL BETWEEN THE INTERIOR AND EXTERIOR THEREOF; A PLURALITY OF AT LEAST THREE TRAY SECTIONS WITHIN SAID SHELL FORMING A VERTICAL SERIES OF CONTACT STAGES, EACH SECTION HAVING A TRAY DECK WITH PASSAGEWAYS FOR THE UPWARD FLOW OF VAPOR AND THE DOWNWARD FLOW OF LIQUID THROUGH THE DECKS ARRANGED TO EFFECT INTIMATE CONTACT BETWEEN SAID LIQUID AND VAPOR WITH A PRESSURE DROP BETWEEN STAGES, SAID TRAY SECTIONS BEING SHAPED TO PERMIT UNIMPEDED VERTICAL MOVEMENT THEREOF AS SEPARATE UNITS THROUGH THE SHELL TO THE TOP THEREOF AND THROUGH SAID TOP OPENING UPON REMOVAL OF SAID CLOSURE; A CLOSED ANNULAR WALL ON EACH TRAY SECTION EXTENDING IN SEALED RELATION FROM THE DECK THEREOF VERTICALLY TO A CORRESPONDING ANNULAR PORTION ON AN ADJACENT SECTION, SAID WALLS ENCLOSING LIQUID AND VAPOR CONTACT SPACES WITHIN THEMSELVES, AND THE WALL AND DECKS OF AT LEAST A PLURALITY OF LOWER SECTIONS HAVING CLEARANCES WITH RESPECT TO THE SHELL TO DEFINE A COMMON OUTER SPACE BETWEEN THE SHELL AND SAID LOWER SECTIONS EXTENDING VERTICALLY THROUGH THE HEIGHT OF SEVERAL TRAY SECTIONS; AN ANNULAR SEAL BETWEEN EACH ANNULAR WALL AND ITS CORRESPONDING ANNULAR PART OF THE ADJACENT SECTION ARRANGED TO PREVENT THE OUTWARD FLOW OF VAPOR FROM SAID CONTACT SPACES INTO SAID OUTER SPACE, EACH SEAL COMPRISING A TROUGH ADAPTED TO RETAIN A POOL OF LIQUID THAT CONTACTS THE INNER AND OUTER SIDES OF THE ANNULAR WALL, WHEREBY SAID SEALS CAN BE ESTABLISHED BY SUCCESSIVELY LOWERING TRAY SECTIONS THROUGH THE SHELL AND SAID CONTACT SPACES CAN BE MAINTAINED AT PROGRESSIVELY DIFFERENT PRESSURES INDEPENDENT OF THE PRESSURE IN SAID OUTER SPACE; SEAL MEANS BETWEEN THE LOWERMOST TRAY SECTION AND THE SHELL CLOSING OFF THE BOTTOM OF SAID OUTER SPACE, WHEREBY THE PRESSURE IN SAID OUTER SPACE IS ISOLATED FROM THE PRESSURE IMMEDIATELY BENEATH THE TRAY DECK OF SAID LOWERMOST TRAY SECTION; AND A VAPOR PASSAGEWAY INTERCONNECTING SAID OUTER SPACE WITH ONE OF THE UPPER CONTACT SPACES, WHEREBY THE PRESSURE IN SAID OUTER SPACE WILL BE THAT OF SAID ONE UPPER CONTACT SPACE. 